A process for the preparation of a polymer nanoparticle by a photoinduced emulsion polymerization includes preparing an emulsion comprising at least one surfactant, a dispersed phase and a continuous phase. The dispersed phase comprises at least one polymerizable monomer and the continuous phase comprises water and at least one photoinitiator. The at least one polymerizable monomer is polymerized by exposing the emulsion to an electromagnetic radiation having a wavelength so as to induce a generation of radicals from the at least one photoinitiator. The at least one photoinitiator is selected from at least one compound of formula (I)